Flooding is as much a part of the legacy of Britannia Beach as mining.
In 1925 a catastrophic flood killed 37 people. A flood of similar magnitude occurred in 1991 when Britannia Creek filled with gravel and jumped its bank near the same place as the 25 flood. And there are fears flooding could happen again.
A one in 200 year flood; an event that can happen when there are rain storms coupled with very high tides, could occur in Britannia. Theres also the potential for a substantial rock slide in Jane Basin.
These hazards were on everyones mind at a third public meeting updating the Britannia Mine remediation project held at the Britannia Beach community hall on May 23. Discussions included flood risk assessment, the location of a water treatment plant and sludge storage options.
Flood risk assessment in Britannia Creek includes maximum probable flood and debris flow analysis. Other activities include site-wide monitoring of surface water conditions in Britannia Creek, Jane Creek, Furry Creek and Mineral Creek.
Peter Healey, an engineer with SRK Consulting in Vancouver, brought the audience up to date on whats been done underground with regard to safety.
"We had to rehabilitate to make it as safe as we possibly could so people could work in there," Healey began.
Work being done inside the mine includes installation of flow monitoring equipment.
"At the plug itself, we installed displacement gauges to measure any minute movement of the plug when were putting pressure on the plug," Healey explained. "Theres a piezometer installed in the host rock just in front of the plug to monitor ground water pressures that could build up within the rock itself as we increase pressure behind the plug. There is also a valve that is a key component controlling the amount of water that flows through the pipe."
The flow rate through the mine is estimated to reach 420 litres per second when the freshet hits in mid-June. The out-flow arrangement can currently handle up to 800 litres per second.
"Water enters up at the Jane Basin area and discharges down at the 4100 level," Healey continued. "During the freshet the system controls its own flows."
Two plug tests are being conducted at the mine.
"The first test was run from March 26 to May 13," Healey continues. "We took that up to 102 metres above the plug and, we drained it down to 20 metres. Were currently maintaining it at 20 metres for safety purposes."
The second test will involve turning a valve off about a week after the freshet, allowing the waters to rise up to about 250 metres above the plug located 300 metres above sea level. As soon as the water hits the 250-metre level the water will be brought back down to a controlled discharge.